Intermediate-temperature solid oxide fuel cells (IT-SOFCs) have garnered much attention in recent years due to their potential to meet cost and reliability targets required of commercial products. Two areas of interest in IT-SOFCs are reducing electrolyte thickness and/or discovering new electrolyte materials with improved ionic conductivity. In searching for new electrolyte materials, proton conducting ceramics emerge as strong electrolyte candidates for IT-SOFCs. Among these proton conductors, yttrium-doped barium zirconate (BZY) has appeal due to its high bulk proton conductivity, excellent chemical stability in CO2 and good mechanical strength. However, this material is refractory and requires a very high temperature (from about 1700° C. to about 2100° C.) and a long sintering time (often greater than 24 hours), even with nanosize starting powders, to achieve a dense microstructure. Higher temperature or longer time often results in a deficiency in barium and other impurity phases, causing high grain-boundary resistance. Although the sintering temperature of BZY can be effectively reduced by adding sintering aids, e.g. NiO, ZnO, MgO, CuO, and Sc2O3, such sintering aids can lead to a lowered ionic conductivity and increased electronic conductivity, especially in reducing atmospheres.
A Li2CO3—K2CO3 eutectic mixture supported by a porous LiAlO2matrix is a standard electrolyte package for molten carbonate fuel cells (MCFCs). The pore size and porosity in the LiAlO2 matrix used by the MCFC industry are carefully tailored so that the molten carbonate phase is retained within the porous LiAlO2 matrix by capillary forces. The pores in LiAlO2 are, therefore, filled with the molten carbonate phase, making the solid/liquid electrolyte membrane gastight.
As such, a need exists for a dense proton conductor membrane that can benefit from such a strategy. Methods of manufacturing such a membrane would also be desirable.